Synthesis of polyisobutylenes carrying either unsaturation or hydroxyl groups at both ends, in the case of a linear polymer, or at all ends in the case of a star polymer structure, e.g., one having at least three polymer arms one end of each is linked to a common nucleus, requires that the polyisobutylene first be telechelic or terminally functional. Second, to avoid separate syntheses from different end groups, it is necessary that the functionality be identical. In this manner synthesis will occur simultaneously at all termini.
Unfortunately, it has not been possible heretofore to prepare certain isobutylenes having identical termini. Prior investigations with other co-workers in the laboratories of the Assignee or record herein have demonstrated that certain unsaturated organic halides in combination with BCl.sub.3 are effective initiating systems for isobutylene polymerization to form asymmetric telechelic polymers i.e., polyisobutylenes having an olefinic head and an alkyl halide end group. These investigations have been published and include: J. P. Kennedy, S. Y. Huang and S. C. Feinberg, J. Polymer Sci., Polymer Chem. Ed. 15, 2843 (1977); J. P. Kennedy, S. Y. Huang and R. A. Smith, Polymer Bulletin 1, 000 (1979); and J. P. Kennedy, S. Y. Huang and R. A. Smith, J. Polymer Sci., Polymer Chem. Ed., (submitted).
At least one U.S. patent of which I am aware, is directed toward a method of forming polyisobutylene having an unsaturated group at each end. That U.S. Pat. No. 3,634,383, discloses the contacting of isobutylene with a 5 A molecular sieve supposedly to extract a hydride ion from the monomer. Despite the claim that a product having two terminal double bonds thereby resulted, I am not aware that this work has ever been successfully duplicated and, in fact, the patentee has more recently stated that the polyisobutylene made by 5 A molecular sieves contained less than two olefinic end groups, i.e., 1.70-1.32, per mole. These results have been published: S. L. Manatt, J. D. Ingham and J. A. Miller, Jr., Organic Magnetic Resoanance, 10, 198 (1977).
With respect to polyhydrocarbon diols, telechelic polybutadiene and polyisoprene diols have been prepared according to a process contained in recent literature: Schnecks, H., Degler, G., Dongonski, H., Caspary, R., Angerer, G. and NG, T. S., Angen. Makromol. Chem., 70, 9 (1978). However, the functionalities of these molecules were only close to but not exactly two. A functionality of exactly 2.0 is mandatory for efficient molecular weight extension by condensation with diisocyanate chemistry.
With respect to polyisobutylene, U.S. Pat. No. 3,392,154 discloses a method of producing saturated rubbery carboxy or hydroxy functional terminated polyisoolefins by reacting a low unsaturated polyisoolefin with ozone then a hydrogen containing compound and finally an oxidizing or reducing agent. The preparation of hydroxy terminated polyisobutylene is also disclosed by R. L. Zapp, G. E. Serniuk, and L. S. Minckler, Rubber Chemistry and Technology, Vol. 43, No. 5, (1970), and involves the direct reduction of carboxy terminated polyisobutylene with lithium aluminum hydride in ethyl ether. The carboxy terminated polymer was in turn prepared by the ozonolytic cleavage of piperylene butyl, set forth in greater detail in the aforementioned patent.
The functionality of these carboxy and hydroxy terminated polymers was not exactly 2.0 as indicated by Table VII of the publication to Zapp et al wherein the carboxy functionality per polymer molecule was represented as 1.91 to 1.96 and as evidenced by the fact that Exxon has prepared and submitted samples of the carboxy terminated polyisobutylene to requesting parties, furnishing descriptions of the polymer product therewith as having a molecular weight of about 1800 and a functionality of 1.95. Also in a publication, F. P. Baldwin, G. W. Burton, K. Griesbaum and G. Hanington, Advances in Chemistry Series, No. 91, 448-464 (1969), F. P. Baldwin being the patentee of U.S. Pat. No. 3,392,154, the carboxy terminated polyisobutylene is described as a liquid rubber with a molecular weight of between 1800 to 3500 and an average functionality of about 1.8 carboxy groups per molecule.
Inasmuch as the conversion of carboxyl groups to hydroxyls cannot increase the average functionality per molecule, which may actually decrease, a dihydroxy terminated polyisobutylene of 2.0 functionality would not be obtained. As stated hereinabove, a functionality of exactly 2.0 is mandatory for subsequent reactions involving the telechelic polymer. And, while these methods exist for adding terminal functionality of more than 1.0 but less than 2.0, none is directed toward terminal functionalities of 3.0 which would be required with star polyisobutylenes.